Final Report Summary - CEFMED (Climate effects on the deep-sea ecosystem functioning of the Mediterranean Sea)
The deep-sea floor ecosystem is one of the largest on the planet, covering roughly 60% of the Earth’s surface. Despite this vast size, our knowledge of the deep sea is poor relative to other marine ecosystems and future effects of human activities, either indirectly through climate changes or directly through exploitation of deep-sea resources are difficult to predict. Nevertheless, the deep sea has one of the highest levels of biodiversity on Earth and the maintenance of this biodiversity is thought to be essential to ecosystem stability and the maintenance of ecosystem services, a prerequisite of human well-being.
Deep benthic and pelagic communities in virtually every deep-sea habitat, feed off organic matter sinking through the ocean interior from the euphotic zone. Although low amounts of nutrients reach the deep-sea floor, the vast area of the ocean floor means that the deep sea is of global significance for carbon, nitrogen and phosphorus cycling. Thus, any changes to upper ocean processes, which eventually modify the flux of this organic matter, will also be manifested in large-scale changes of deep-sea diversity, ecosystem processes, stability and resilience. Hence, climatic changes affecting surface ocean processes and anthropogenic interventions may have a direct impact on deep-ocean ecosystems.
Under this contexts, CEFMED set out to investigate the impact of climate-driven changes in megafaunal communities (invertebrates) in the deep sea. In particular, during the two years of the project, a series of complex experiments were set up in order to investigate how food supply influences key megafaunal organisms in the deep sea and how the presence of these organisms influences the rates and pathways of organic matter (OM) degradation. The results of the project will provide the necessary information to increase our understanding on how food quantity and quality relates to carbon processes, which in turn will enhance our ability to predict how climate will influence responses of deep-sea communities and related ecosystem services under different climate change scenarios.
The objectives of CEFMED were:
1. To investigate the role of key megafaunal species in the ecosystem
2. To investigate the physiological responses of key megafaunal organisms to a varying quality and quantity of food input
3. To investigate the impact of key deep-sea megafauna on the uptake of carbon in macro- meio- and microbial fauna
4. To predict the impact of climate-driven changes in response to food by means of a model
Field work
The field work of CEFMED was carried out in collaboration with HCMR and JAMSTEC, during three deep-sea cruises with the R/V YOKOSUKA and the submersible SHINKAI 6500. During these three cruises, replicated video transects were conducted with the submersible in order to identify and estimate densities of key megafaunal organisms. Subsequently, two different in situ experiments were performed at 5257 m depth in order to measure both the physiological response of the megafaunal organisms, but also to investigate the response of the benthic community to the quantity and quality of organic matter input in two different locations (1. Oligotrophic, 2. Eutrophic). The physiological response was investigated by analysing lipids, the isotopic composition of fatty acids and phytopigments from different tissues of the megafauna, mainly deep-sea holothurians. The response of the benthic communities to different food-pulses was investigated by quantifying the uptake of 13C and 15N by the different components of the benthic community (meio-, macro- and megafauna).
Some key findings of CEFMED include:
Although some of the analysis are still ongoing, preliminary key findings so far include:
1. Macrofrauna community was significantly more abundant in the eutrophic region, than in the oligotrophic region There were also significant differences in density between the two regions. Simper analyses revealed that Nematoda and Copepoda were responsible for 47% and 14% of the variation in density between both regions, respectively.
2. Nematoda was the dominant taxon in the eutrophic region contributing 71% to the total abundance. Arthropoda was the second most abundant group, contributing with 13%. As for the oligotrophic region, Arthropoda was the dominant taxon contributing 38% to the total abundance. Nematoda was the second most abundant group, contributing with 36%.
3. In the eutrophic region, the lowest 15N/13C values were attributed to organisms that could not be identified plus Sabellidae but most of them were filter-feeders. The organisms with the highest % of 15N belonged to Holothuridae and Sipunculidae (sub-surface deposit feeder, predators). In the oligotropic region, the lowest 15N/13C values were also attributed to organisms that could not be identified, plus Nematoda with most of them being again filter feeders. The organisms with the highest % of 15N belonged to Holothuridae and Phyllodocidae (sub-surface deposit feeder, predators).
4. Both experiments investigating the response of macro- and megafauna to different food sources revealed that the two time intervals used for the incubations (short and long) were either too short or too long for most of the macrofauna assemblage. Nevertheless, although the data obtained were neither strong or consistent to distinguish between feeding preferences, it appears that diatoms are the favourite food source for the eutrophic region. However, a new set of in situ experiments needs to be planed with different times of incubation.
Expected final results and potential impact of the project
The results of CEFMED are very diverse and will include at least 3 peer-reviewed papers. Although data analysis is still in progress, the results of CEFMED so far clearly indicate that food quantity plays an import role in structuring benthic fauna standing stocks. They also demonstrated the capability of different responses to the addition of food, as well as an active food selection by most of the taxa studied. On the other hand, diatoms appear to be the most important food source for most components of the benthic community.
After further data analysis and integration of all the results obtained from the project a model will be build to examine how the benthic food web is influenced by the differences in food supply and how much C (and N) is removed by the benthic fauna. Such processes are important to modulate atmospheric CO2 levels and calcite saturation levels in the ocean.
Clearly more observations and in situ deep sea experiments are required. Nevertheless, it is concluded that the experimental design combining in situ deep-sea technology and stable carbon and nitrogen isotope labeling proved to be very useful in investigating benthic carbon turnover on the community level.
Deep benthic and pelagic communities in virtually every deep-sea habitat, feed off organic matter sinking through the ocean interior from the euphotic zone. Although low amounts of nutrients reach the deep-sea floor, the vast area of the ocean floor means that the deep sea is of global significance for carbon, nitrogen and phosphorus cycling. Thus, any changes to upper ocean processes, which eventually modify the flux of this organic matter, will also be manifested in large-scale changes of deep-sea diversity, ecosystem processes, stability and resilience. Hence, climatic changes affecting surface ocean processes and anthropogenic interventions may have a direct impact on deep-ocean ecosystems.
Under this contexts, CEFMED set out to investigate the impact of climate-driven changes in megafaunal communities (invertebrates) in the deep sea. In particular, during the two years of the project, a series of complex experiments were set up in order to investigate how food supply influences key megafaunal organisms in the deep sea and how the presence of these organisms influences the rates and pathways of organic matter (OM) degradation. The results of the project will provide the necessary information to increase our understanding on how food quantity and quality relates to carbon processes, which in turn will enhance our ability to predict how climate will influence responses of deep-sea communities and related ecosystem services under different climate change scenarios.
The objectives of CEFMED were:
1. To investigate the role of key megafaunal species in the ecosystem
2. To investigate the physiological responses of key megafaunal organisms to a varying quality and quantity of food input
3. To investigate the impact of key deep-sea megafauna on the uptake of carbon in macro- meio- and microbial fauna
4. To predict the impact of climate-driven changes in response to food by means of a model
Field work
The field work of CEFMED was carried out in collaboration with HCMR and JAMSTEC, during three deep-sea cruises with the R/V YOKOSUKA and the submersible SHINKAI 6500. During these three cruises, replicated video transects were conducted with the submersible in order to identify and estimate densities of key megafaunal organisms. Subsequently, two different in situ experiments were performed at 5257 m depth in order to measure both the physiological response of the megafaunal organisms, but also to investigate the response of the benthic community to the quantity and quality of organic matter input in two different locations (1. Oligotrophic, 2. Eutrophic). The physiological response was investigated by analysing lipids, the isotopic composition of fatty acids and phytopigments from different tissues of the megafauna, mainly deep-sea holothurians. The response of the benthic communities to different food-pulses was investigated by quantifying the uptake of 13C and 15N by the different components of the benthic community (meio-, macro- and megafauna).
Some key findings of CEFMED include:
Although some of the analysis are still ongoing, preliminary key findings so far include:
1. Macrofrauna community was significantly more abundant in the eutrophic region, than in the oligotrophic region There were also significant differences in density between the two regions. Simper analyses revealed that Nematoda and Copepoda were responsible for 47% and 14% of the variation in density between both regions, respectively.
2. Nematoda was the dominant taxon in the eutrophic region contributing 71% to the total abundance. Arthropoda was the second most abundant group, contributing with 13%. As for the oligotrophic region, Arthropoda was the dominant taxon contributing 38% to the total abundance. Nematoda was the second most abundant group, contributing with 36%.
3. In the eutrophic region, the lowest 15N/13C values were attributed to organisms that could not be identified plus Sabellidae but most of them were filter-feeders. The organisms with the highest % of 15N belonged to Holothuridae and Sipunculidae (sub-surface deposit feeder, predators). In the oligotropic region, the lowest 15N/13C values were also attributed to organisms that could not be identified, plus Nematoda with most of them being again filter feeders. The organisms with the highest % of 15N belonged to Holothuridae and Phyllodocidae (sub-surface deposit feeder, predators).
4. Both experiments investigating the response of macro- and megafauna to different food sources revealed that the two time intervals used for the incubations (short and long) were either too short or too long for most of the macrofauna assemblage. Nevertheless, although the data obtained were neither strong or consistent to distinguish between feeding preferences, it appears that diatoms are the favourite food source for the eutrophic region. However, a new set of in situ experiments needs to be planed with different times of incubation.
Expected final results and potential impact of the project
The results of CEFMED are very diverse and will include at least 3 peer-reviewed papers. Although data analysis is still in progress, the results of CEFMED so far clearly indicate that food quantity plays an import role in structuring benthic fauna standing stocks. They also demonstrated the capability of different responses to the addition of food, as well as an active food selection by most of the taxa studied. On the other hand, diatoms appear to be the most important food source for most components of the benthic community.
After further data analysis and integration of all the results obtained from the project a model will be build to examine how the benthic food web is influenced by the differences in food supply and how much C (and N) is removed by the benthic fauna. Such processes are important to modulate atmospheric CO2 levels and calcite saturation levels in the ocean.
Clearly more observations and in situ deep sea experiments are required. Nevertheless, it is concluded that the experimental design combining in situ deep-sea technology and stable carbon and nitrogen isotope labeling proved to be very useful in investigating benthic carbon turnover on the community level.